Oxygenator



Oct. 16, 1962 c. R. BROMAN OXYGENATOR Filed April 22, 1957 i Jig/ZATTORNEYS.

United States Patent f 3,053,464 OXYGENATGR Cyrus R. Broman, Evanston,Ill, assignor to Baxter Laboratories, Inc., Morton Grove, Ill., acorporation of Delaware Filed Apr. 22, 1957, Ser. No. 654,161 3 Claims.(Cl. 128-214) This invention relates to an improvement in an oxygenator,and more particularly to an oxygenator employed for treating human bloodas a substitute for the human heart and lungs.

Reference is made hereby to the co-owned application of Theodore H.Gewecke and myself, Serial No. 610,605 filed September 18, 1956, whichdiscloses an oxygenator on which this invention is an improvement.

Oxygenating devices for human blood have been well known to the medicalart for centuries. As such they have taken many forms. Despite thevariety of forms available, ranging from the most simple to the verycomplex, such devices have found relatively little use. Since thesedevices deal with one of the most delicate parts of the human anatomy,there is always the fear that they will not prove to be perfectlyoperative. The fears of doctors in the use of oxygenating devices have,to a very large extent, been focused on the oxygen dispersing mechanismitself. This particular structural element, i.e., the oxygen dispersingmeans, must be the equivalent of the human lungs. The human lungsoperate to provide the proper amount and distribution of oxygen toachieve carbon dioxide exchange.

Finding a full and operative structural equivalent of the human lungshas been an important problem facing those working in the art ofartificial oxygenation of blood. The amount of oxygen, contacted withthe blood is critical. Too much oxygenation in an artificial oxygenatorcauses excessive foaming of-the blood which may persist even when theblood is reinfused into the patient, giving rise to the danger of anembolism. Even if the oxygenator is provided with adequate means fordefoaming, the presence of-excess foam necessarily restricts theefiiciency of the oxygenating device and, more importantly, itscapacity. On the other hand, an insufficient quantity of oxygen comingin contact with the blood gives rise to an insufficient carbon dioxideexchange so that the blood is not properly revived.

Even though the amount of oxygen brought in contact with the blood isproper, i.e., not promotive of excessive foaming but yet sufiicient tofully oxygenate the quantity of blood passed through the oxygenatingdevice it is further necessary and equally important that thedistribution of the oxygen quantity be proper. Generally, an improperdistribution of oxygen increases the turbulence of the blood andincreases the rate of hemolysis of red blood cells.

It is therefore a general object of this invention to provide an oxygendispersing device for a blood oxygenator which overcomes the problemsoutlined above. Another object is to provide a device for dispersingoxygen wherein the undesirable effects of blood turbulence aresubstantially avoided. Still another object is to provide an oxygendispersing device for introducing oxygen into a vertically disposed,blood filled chamber. Yet another object is to provide a device forintroducing oxygen into a vertical column of blood wherein a largenumber of small bubbles of oxygen are provided. A further object is toprovide an oxygen dispersing device capable of introducing a largenumber of small but uniformly sized bubbles into the bottom of a columnof blood. Other objects and advantages of my invention will be seen asthis specification proceeds.

3,358,464 Patented Oct. 16, 1962 This invention will be described, in anillustrated embodiment, in conjunction with the accompanying drawing, inwhich- FIGURE 1 is an elevational view of a disposable blood oxygenatorincorporating the improved features of this invention; FIGURE 2 is anenlarged cross sectional view taken along the line 2-2 of FIGURE 1; andFIGURE 3 is a top plan view of the oxygen dispersing device shown incross section in FIGURE 2.

Referring now to the drawing, an illustration is given of a disposableblood oxygenator in FIGURE 1. The oxygenator in FIGURE 1 is designatedgenerally by the numeral 11 Oxygenator 10 includes two substantiallyrectangular fiat sheets of a plastic material of a thermo plasticcharacter, such as polyvinyl chloride. Two such sheets are arranged inface-to-face, lay flat relation and are heat-sealed along a number oflines to form a unitary structure, the details of which are set forthmore particularly in the above identified application of Theodore H.Gewecke and Cyrus R. Broman. The sheets making up oxygenator 10 are heatsealed along two, spaced, longitudinally disposed, parallel lines 11 and12 to form an oxygenation or bubbling chamber or column, designated 13.The sheets are additionally heat sealed along two, horizontallydisposed, spaced, parallel lines 14 and 15 adjacent one end thereof(ultimately providing the top of the oxygenator) to provide a slot 16adapted to receive a slip metal rod (not shown) which provides aconvenient suspending means for the oxygenator.

In the illustration given, the sheets making up oxygenator 10 areadditionally heat sealed together along a series of line (convenientlyidentified as V configurations). For example one V configuration of heatsealing designated by the numeral 17 has its apex laterally disposed anddirected away from oxygenation chamber 13. A second V heat sealconfiguration 18 is oppositely oriented to configuration 17 while athird configuration 19 is disposed similarly to configuration 17. Thus,a defoaming chamber 20 is provided in the topmost portion of oxygenator10 which communicates with oxygenation chamber 13. The spaced heat sealsdesignated by the numerals 17, 18 and 19 provide a zig-zag or serpentineoutlet passage from the bottom of defoaming chamber 20, the outletpassage being designated by the numeral 21.

A series of bubble bafiles or weirs 22 are provided in passage 21 at thepoints where the outflow or blood changes direction. Oxygenator 10 isalso provided with a thermostat element pocket 23 extending into passage21 which is adapted to receive a suitable thermostatic element (notshown).

The extreme end portion of the outlet passage 21 is provided with ablood filter 24. The last leg of the serpentine passage 21 is defined byone leg of V configuration 19 and an additional linear heat seal 19a.Oxygenator 10 is provided with a pair of holes extending therethroughand designated 25 which provide convenient means for tying theoxygenator in place so as to maintain it in a substantially flatcondition during use. The upper end of the oxygenator is provided with agas outlet port 26 which serves to vent excess oxygen and carbon dioxideto the atmosphere.

The bottom portion of oxygenator 10 is partially heat sealed along ahorizontal line as designated by the numeral 27 to close-off the bottomportion of oxygenation chamber 13. Heat sealed into seal 27 is bloodinlet tube 28 and oxygen inlet tube 29, oxygen inlet 29 terminating inan oxygen dispersing device generally designated 30 and shown moreparticularly in FIGURES 2 and 3. Also associated with oxygenator 10during .operation thereof, but not shown herein, are suitable pumps andtubing communicating oxygenator with the body of a patient whose bloodis undergoing oxygenation.

For placing the oxygenator 10 in use certain additional materials areneeded. These include a rod and suitable stand for supporting oxygenator10 by means of sleeve or chamber 16. Two pumps are required for inducingflow to and from oxygenator 10. One pump is for the venous line whichterminates in blood inlet 28 and another pump is required for thearterial line which is attached to the oxygenated blood outletdesignated 31. Additional tubing for connecting oxygenator 10 with thepatient is also required. A source of heat such as a bank of three 150watt heat lamps placed about 12 to 18 inches from the unit is required.These lamps are operated by a suitable thermostat and relay which can beassociated with oxygenator 10 as by insertion into pocket 23.

The use of oxygenator 10 can be further appreciated from a considerationof a typical operating procedure such as is set forth immediately below.

Operation Inasmuch as oxygenator 10 is intended for single use, a quickset-up procedure is contemplated. First, oxygenator 10 is suitablysuspended by a rod extending through chamber or sleeve 16 and tied downby laces extending through holes 25 at the bottom of oxygenator 10.Thereafter and 125 cc. of 0.9% sodium chloride solution (normal saline)is introduced upwardly into oxygenator 10 through arterial line 31,thereby filling an enlarged chamber 32 which serves as a slowndownchamber. Thereafter any bubbles are removed from the saline solution asby gentle manipulation. Outlet passage 21 is subjected to heat for abouttwo or three minutes and about 1,000 cc. of heparinized blood isintroduced into bubbling chamber 13 through venous line 28 to filloxygenator 10 to blood operating level 32 which exists in defoamingchamber 20. Previous to the introduction of the heparinized blood,oxygen from a source not shown is introduced into chamber 13 by means ofoxygenation tube 29. The arterial and venous lines 31 and 28respectively are now connected to suitable pumps (not shown) and furthercommunicated to the blood vessels of a patient as by cannulation. Thepatient has been administered 150 U.S.P. heparin units per kilogram ofbody Weight. The priming blood contains about 4000 U.S.P. heparin units.

When the pumps are started after proper connection, venous blood flowsfrom the venous pump through the venous inlet tube and into the bubblingchamber. Oxygen from an outside source flows through the oxygen inlettube 29 and mixes with the blood in the oxygenation chamber 13.Thereafter, chamber 13 is gradually filled with a gentle, uninterrupted,rising column of bubbles. As the bubbles reach the top of chamber 13,they flow into the defoaming chamber 20. There the bubbles come incontact with the siliconized walls of chamber 20 and are graduallydispelled. Carbon dioxide and excess oxygen through vent at the uppercorner of chamber 20.- Oxygenated blood falls into the pool defined byoperating level 32 and the top leg of V configuration heat seal 17.Thereafter, blood exists from the pool, traveling slowly down thezig-zag outlet passage 21 toward the arterial line 31. Any remaining.bubbles coming from the blood in passage 21 rise in passage 21 andeventually exist through vent 26: Bafiies 22 provide for bubbles totransfer from one leg of passage 21 to another without being swept backdown with blood flow, thus facilitating complete stripping of'blood ofany occluded bubbles. The descending channel of passage 21 widens justabove filter chamber 24, as designated 23a, to permit any pinpointbubbles to aggregate, if any have proceeded this far. The oxygenatedblood then flows downward to filter 24 where clots or particulate matterare eliminated. The blood continues through the filter 24', out througharterial- 4 line 31 to the arterial pump and then to the subject. Aftercompletion of surgery involving the use of oxygenator 10, any residualblood in oxygenator 10 can be pumped out for reuse.

In order to provide the not only desirable but critical distribution ofoxygen bubbles, oxygen defusing device 30 is employed. In FIGURE 2device 30 is seen to include a tubular member 33 which is connected atone end thereof to venous line 29. The connection between tubularelement 33 and line 29 can be readily achieved by heat sealing sincepreferably element 33 is also constructed of polyvinyl chloride, as isthe tubing defining venous line 29.

The end of element 33 opposite the end connected to line 29 is providedwith an enlarged portion 34 and the flow passage existing within tubularelement 33 generally conforms to the outside configuration of element33, the fiow passage being designated 35. The enlarged portion oftubular element 33 is closed by a diaphragm 36 extending across passage35 at the end of tubular element 33. Diaphragm 36 is provided with aplurality of holes 37 (best seen in FIGURE 3) which are uniformlydistributed in diaphragm 36 and which are of uniform size. Oxygendiffusing device 30 is so constructed that it can he heat sealed intoseal 27 so as to maintain diaphragm 36 in substantially horizontalcondition.

Excellent results have been obtained when diaphragm 36 is alsoconstructed of polyvinyl chloride, thereby permitting connection ofdiaphragm 36 to tubular element 33 by heat sealing. Where diaphragm '36is attempted to be connected to element 33 by solvent sealing, a greaterthickness of diaphragm is required since a portion of the diaphragm isdissolved in order to effectuate the seal. The greater thickness ofdiaphragm makes substantially more difficult the provision of uniformsized holes 37 therein. Optimum results have been obtained by using athickness of polyvinyl chloride of about 4 mils as diaphragm 36.

For the flow rates generally required in oxygenation of blood of humanpatients, which range from about 2 /2 to 4 liters of oxygen for eachliter of blood, and enlargement of fiow passage 35 of a diameter ofabout /8 of an inch has proved desirable. Across this opening, diaphragm36 is provided with openings of about 10 mils diameter disposed on Xinch centers.

I have found that the horizontal disposition of diaphragm 36 isimportant in minimizing blood hemolysis. Also important is the provisionof uniform sized openings 37 in diaphragm 36. Where openings arenon-uniform, the presence oflarger openings causes increased hemolysisdue to excessive turbulence and uneven distribution of 0 Also, oversizedopenings'where the openings are non-uniform reduces the oxygen pressureapplied to the under surface of diaphragm 36 so that blood may run backinto oxygen tube 29. It is to be appreciated that this cannot beconveniently overcome by increasing the pressure of oxygen since thiswould provide a flow rate higher than the desired flow rate and therebyincrease turbulence and hence hemolysis. On the other hand, if theopenings are too small, an intermittent flow of bubbles is providedwhich results in jetting, resulting not only in turbulence butinadequate oxygenation of blood.

With the increased usage of blood oxygenators under the influence ofworkers such as-Dr. C. Walton Lillehei of the University of MinnesotaMedical School, and others, the problem of controlling oxygen-bloodcontact has become even more acute. With greater numbers of heartoperations in prospect, it is mandatory that the artificial heart-lungsemployed be free of any structural defects. As pointed out above, thesedefects have been considered essentially to relate to the phase ofoxygenator operation dealing with oxygen-blood contact. Improvementshave been presented that deal with the phase of contact wherein gases'have been stripped from the blood after contact but it is to beappreciated that an equally important problem exists with respect to theinitiation of contact and the diffusion of oxygen in the blood.

In this connection it is to be further appreciated that with theincreased number of heart operations that are being performed, it isnecessary to provide oxygenators that are not only foolproof inoperation but which are easily and reasonably constructed. Many heartsurgical operations would not be performed if the oxygenator apparatusis too costly or too complicated to employ since hospitals may feel itundesirable to stock expensive devices. The improvement presented hereineminently fills this need by making available an oxygenator which can bereasonably and quickly constructed. An important operative element ofoxygenator 10, is oxygen dispersing device 30 Which can be readily andquickly assembled by heat sealing to provide a unit capable of foolproofoperation.

While in the foregoing specification an embodiment of the invention hasbeen set out in considerable detail for purposes of illustration, itwill be apparent to those skilled in the art that considerable deviationin these details may be made without departing from the spirit andprinciples of the invention.

I claim:

1. In combination with a disposable oxygenator constructed of a pair ofthermoplastic sheets arranged in face-to-face relation and unitedtogether to form a vertical oxygenation chamber therein when the unitedsheets are disposed vertically, a tubular member secured in the base ofsaid chamber and providing .a conduit for oxygen to enter said chamber,said tubular member having ends internal and external of said chamber,said external end being adapted to be connected to an oxygen source, thesaid internal end being enlarged, a diaphragm extending across the saidinternal end to close the same, said diaphragm being provided with aplurality of uniformly sized openings extending therethrough, saidopenings being uniformly distributed in said diaphragm.

2. In an oxygenator, a vertically-extending oxygenating chamber definedby a pair of thermoplastic sheets perimetrically united along the sidesand bottom, the bottom union being interrupted at two spaced points, aconduit extending through said union at each of said points to deliverblood and oxygen to said chamber, the oxygen delivery conduit beingequipped internally of said chamber with an upwardly-flared fitting, anda diaphragm secured to the upper end of said fitting, said diaphragmbeing equipped with a plurality of uniformly sized openings extendingtherethrough, said openings being uniformly distributed in saiddiaphragm.

3. The oxygenator of claim 2 in which said diaphragm is constructed ofthermoplastic material.

References Cited in the file of this patent UNITED STATES PATENTS1,890,692 Mahan Apr. 14, 1931 2,708,648 Ulmschncider May 17, 19552,774,628 Engstrum Dec. 18, 1956 2,804,419 De Woskin et a1. Aug. 27,1957 2,833,279 Gollan May 6, 1958 2,854,002. De Wall et a1 Sept. 18,1958 FOREIGN PATENTS 255,262 Great Britain July 22, 1926 OTHERREFERENCES Gott et al.: A Self-Contained, Disposable Oxygenator, Thorax(London), vol. 12, N0. 1, March 1957, pp. 1-9. (Copy available in Div.55.)

Clowes et al.: Pump Oxygenator for Complete By- Pass of Heart, Lung,from Surgery, vol. 36, N0, 3, September 1954 (pp. 560-562 relied on).

2. IN AN OXYGENATOR, A VERTICALLY-EXTENDING OXYGENATING CHAMBER DEFINEDBY A PAIR OF THERMOPLASTIC SHEETS PERIMENTRICALLY UNITED ALONG THE SIDESAND BOTTOM, THE BOTTOM UNION BEING INTERRUPTED AT TWO SPACED POINTS, A